I wouldn't write Bitcoin off so fast. Whenever a new technology comes along the vested interests try and make it conform to the existing systems. Like England requiring motor cars to have a driver, an engineer and a flag man to walk in front and warn people of the coming danger. 

If we fragment off into smaller crypto currencies, the small ones will become subject to currency manipulation and lose value over time as the number of crypto currencies continues to grow. 

The battle needs to be for Bitcoin.

If 90% of miners and nodes signalled an upgrade the banks would have to follow or hold a dead chain. 

Miners want more transactions on chain. Users want permissionless payments without a bank. When the pain comes, nodes will flag to upgrade, unless they have been persuaded to give up.

Banks would need to subsidise miners and fund expensive misinformation campaigns to stop Bitcoin developing in a way that maintains a peer to peer permissionless protocol. This would be expensive and increase costs which won't be sustainable long term. 

https://m.youtube.com/watch?v=5ca70mCCf2M